Think of someone who is unable to express emotion. Maybe they grew up with the “stiff upper lip” theory of life or maybe they don’t want to upset or annoy someone by saying the wrong thing at the wrong time so they just say and express nothing at all. Whatever the background story, plan a character who can not express any emotions. At least not in words.
How does a person conditioned to be remote and expressionless reveal their emotions, in spite of themselves? What kind of body language do they have that will not show in their face (as they keep their face expressionless)?
Describe how this person changes as they become happy about a winning lottery ticket only to become very unhappy once someone points out the ticket was for a different month and does not have the right numbers after all.